Multiple compartment grinding mills



Jan. 17, 1967 G. o. VERCH MULTIPLE COMPARTMENT GRINDING MILLS Filed March 8, 1965 W/YW/ awn/1,44%");

United States Patent F 3,298.619 MULTIPLE COMPARTMENT GRINDING MILLS George 0. Verch, West Allis, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Mar. 8, 1965, Ser. No. 437,746 8 Claims. (Cl. 241179) This invention relates to multiple compartment grinding mills that are utilized to achieve more than one stage of particle size reduction within a single machine and in particular to a Wall construction dividing a mill shell into separate grinding compartments.

According to a practice of the prior art a grinding mill having a cylindrical shell is internally divided into compartments by an internal division head assembly comprising a spider defined by a ring secured to the inner circumference of the shell and radial arms projecting inwardly of the ring a distance less than the radius of the ring to provide an annular spider framework for the division head assembly. An annular screen asembly is arranged on ea ch side of the spider. Each of the annular screens is made up of a plurality of segmental sector shaped plates, some or all of which are perforated. The plates are secured to the-spider by bolts parallel to the central axis of the mill shell and each of which pass through a plate on each side of the spider to draw such plates toward each other and tightly against the spider therebetween. Pads and/or shims are required to be fitted between adjacent radially extending edges of the plates to prevent a hammering action between adjacent plates when the mill is rotated. Extended operation of the mill causes the plates to become loose and the mill must then be opened in order to gain access to the aforementioned axially extending bolts, the pads and the shims in order to eliminate the looseness and resulting hammering action between parts of the division head assembly. The principal object of the present invention is to pro vide a new and improved division head assembly including plates such as have been described but which can be tightened to eliminate looseness and hammering action of the plates without requiring access to the interior of the mill.

Another object of the present invention is to provide a new and improved mill in which plates such as have been described can all be tightened from the exterior of the mill by adjusting a single bolt projecting radially outward through the shell of the mill.

According to a preferred embodiment of the present invention the radially inner portion of each plate is connected to the spider by a bolt passing therethr-ough parallel to the central axis of the mill. The opening in the plates through which these bolts pass is a slot transverse to the radially extending edges of the plate and transverse to the peripheral edges of each plate. With this arrangement the radially inner portion of each plate is held against the spider but can shift in a plane parallel to the spider. The radially outer portion of each plate is provided with a pivot lug that projects radially outward of the plate along one of the radially extending edges of the plate. The outer surface of this pivot lug engages the inner periphery of the mill shell or a line-spacer arranged within the shell. The outer surface of this lug is a curved surface having a radius considerably less than the radius of the inner surface of the shell so the lug can pivot with a rocking movement relative to the mill shell. The slot of the bolt-slot connection, that has been described as holding the radially inner portion of each plate to the spider, is approximately norm-a1 to the projecting pivot lug and therefore the Walls of the slot act as cam surfaces to guide movement of the radially inner portion of each plate in an are about the pivot lug. In order to pivot such a plate in the manner described without openice ing the mill, a radially extending bolt is connected to each plate and the bolt projects radially outward through the mill shell. Leverage for pivoting the plate with such a bolt is provided by connecting the bolt to the plate at a location circumferentially spaced from the pivot lug. That is, the pivot lug may project radially outward along one of the two radial edges of the plate and the bolt along the other edge.

The plates in the ring are interlocked to provide an annular wall. Each plate edge, along which the pivot lug projects, is notched to define a first wedge surface at an angle transverse to the plate edge. The edge of a neighboring plate, adjacent such a notched edge, is provided with a wedging lug having a second Wedge surface. The wedging lug projects from one plate into the notch of an adjacent plate and the first and second wedge engage. When a suitable device, such as a threaded nut, is turned on the end of the bolt projecting outwardly of the mill shell the bolt is drawn outwardly and pulls on the attached plate to pivot the plate about the pivot lug. As the plate moves, the wedging lug pushes the lug wedge surface against the wedge surface defined by the notch in the adjacent plate. The push on this adjacent plate will be transmitted to the next adjacent plate and so on around the entire ring of plates until the relative movement between the engaging wedge surfaces wedges all plates in a tight ring. Thus by turning the nut on one or more of the bolts projecting outwardly the mill shell plates can be tightened without opening the mill.

Other objects and how they have been attained appear from the following more detailed description with reference to the drawings in which:

FIG. 1 is a view in cross section through a grinding mill according to the present invention; and

FIG. 2 is an enlarged fragmentary view taken along line IIII of FIG. 1 taken in the direction indicated by the arrows.

Referring to the drawing, a cylindrical mill shell 1 is shown fitted with an internal division head assembly including a spider 2. The spider 2 has .ring 3, shown in FIG. 2 to be generally U-shaped in cross section. A spacer 4 of a soft metal, such as zinc, shown in FIG. 2, is inserted between the outer surface of the ring 3 and the inner surface of the shell 1. As shown with broken lines in FIG. 1, the spider 2 has radial arms 5 projecting inwardly of ring 3 a distance less than the radius of the .ring 3. The radially inner ends of arms 5 are connected to a collar 6 having aninner edge 7 and an outer edge 8. The ring 3, arms 5 and collar 6 define the spider 2 and provide an annular framework spider. A vaned cone piece 9 is arranged with an apex 10 projecting axially through the central opening defined by the inner edge 7 of collar 6. The cone piece 9, however, has an outer edge 11 of greater diameter than the central opening defined by collar '6. A segmented annular clamping ring 12 has an outer edge 13 that also has a greater diameter than the central opening defined by collar 6. As shown in FIG. 1, edge 11 is behind collar 6 and edge 13 is in front of collar 6 thus sandwiching collar 6 between a portion of cone piece 9 and clamping ring 12. Bolts 14 connect cone piece 9 and clamping ring 12 to clamp the inner edge 7 of collar '6- therebetween.

The structure that has been described provides the structure needed to support (see FIG. 2) a pair of annular screen assemblies 14, 15 and divide the shell 1 into separate grinding compartments 16, 17.

Referring again to FIG. 1, the annular screen assemblies are made up of a plurality of sector shaped plates 20 spaced apart by soft metal spacers 21, preferably :made of zinc. In a mill for wet grinding all plates 20 on both sides of spider 2 are provided with perforations 22. In a mill for dry grinding all plates are perforated on the feed side of the spider but on the discharge side only a pair of diametrically opposite plates would be perforated and the other plates on the discharge side would be imperforate. The perforations 22 are of course of such size as to pass only particles of less than a predetermined size from compartment 16 to compartment 17.

The plates 20 are attached to the described structures in a manner that will now be described.

The radially inner portion of each plate 20 is con nected to collar 6 of the spider 2 by a bolt 25 passing therethrough parallel to the central axis of mill shell 1. The opening in plates 20, through which bolts 25 pass, is a slot 26 transverse to arms and transverse to the edges 7, 8 of collar 6. Thus when bolt 25 holds a plate 20 against the collar 6, the plate can nevertheless shift parallel to spider 2 within the limits of relative movement between the bolt 25 and the walls defining slot 26.

The radially outer portion of each plate 20- is provided with a pivot lug 27 having a curved outer surface 28. The surface 28 has a radius much less than the radius of the mill shell to provide for a rocking-pivotal movement in the plane of screen assembly 14 and relative to the shell 1. Interposed between surface 28 of pivot lugs 27 and the mill shell 2 are arcuate spacers 30 providing a surface 31 parallel to the mill shell 1 and as shown in FIG. 2 a surface 32 at an angle to the mill shell 1 and parallel to a similarly angled outer peripheral surface 33 of the adjacent plate 20.

Means will now be described for pivoting a plate 20 about a pivot lug 27 in the radial plane of screen assembly 14. As shown in FIG. 2, a bracket 36 is attached to the side of plate 20 that contacts arms 5 of the spider assembly 2. A bolt 38 passes radially through bracket 36, ring 3, spacer 4 and mill shell 1. A nut 40 is turned on the threaded end of bolt 38 projecting outwardly of shell 1. As shown in FIG. 1 the bracket 36 and pivot lug 27 for each plate 20 are spaced apart from each other to provide leverage when pivoting plate 20 in a manner that will be hereinafter described.

Means provided to interlock each of the plates 20 in the annular screen assembly 14 will now be described. The radial edge of each plate 20, along which a pivot lug 27 projects, is notched to define a wedge surface 42 that begins at the edge of a plate 20 and slopes deeper into the plate with the notch being deepest at the radially innermost end of surface 42. The edge of each plate 20 adjacent a notched wedge surface 42 is provided with a wedging lug 43 having a wedging surface 44. Each wedging lug 43 projects into the notch defined by surface 42 of an adjacent plate 20 and surfaces 42, 44 engage.

In the operation of a grinding mill according to the present invention, after continued operation has caused plates 20 to become loose and hammer together, the plates 20 can be tightened without opening the mill in a manner that will now be described. Turning a nut 40 to pull bolt 38 radially outward will pull the side of plate 20, from which the wedging lug 43 projects, radially outward. This movement will pivot plate 20 about pivot lug 2.7. Bolt 25 through the radially inner portion of plate 20 does not prevent such movement because bolt 25 passes I through an opening 26 in plate 20 that is slot shaped and angled to provide for movement of plate 20 through a small segment of an are about pivot lug 27. As a plate 20 moves in this manner the wedging lug 43 projecting therefrom pushes its wedge surface 44 against notch wedge surface 42 and surfaces 42, 44 slide relative to each other. This push by a wedging lug 43 moves the plate 20 being pushed which in turn moves the next plate and so on around the entire ring of plates in assembly 14. Continued turning of a nut 49 in the described manner willcontinue the described movement of the plates 20 until the relative movement of and between engaging wedge surfaces 42, 44 wedge all plates 20 in assembly 14 in a tight ring. An angle between surfaces 42, 44 and the adjaoent radial edges of neighboring plates of about 30 degrees is satisfactory for the described action.

Since the bolts '38 are not in the same radial plane of plates 20, but in a plane axially spaced therefrom, the radial pull on a bolt 38 has an axial component in the direction toward the spider 2 and hence in addition to the described pivotal movement of a plate 20, the plate is also drawn tight against the spider.

It is also a particular advantage to have bolts 38 near the leading edge of a plate and pivot lug 27 near the trailing edge. Note in FIG. 1 that arrows indicate the mill turning clockwise.) Material 49 between annular screens 14, 15 will, of course, always collect in the trailing pocket, as indicated in FIG. 1. A separately replaceable wear plate 50 is therefore provided in that location. This pocket defined by wear plate 50 between assemblies 14, 15 will be substantially empty by the time it reached a three or four oclock position on the down turning side and does not begin to fill again until just before resuming upward movement (because the entire charge in the mill has a contour as indicated with a broken line 51). Bracket 36, a triangular flange 5a (joining spider arms 5 to ring 3), and the leading position of bolts 38 are features that all combine to protect bolts 38 from wear resulting from impact with abrasive charge material.

From the foregoing it will be understood that the present invention is possessed of unique advantages. However, such modifications and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included within the scope of this invention and thus the scope of this invention is intended to be limited only by the scope of the claims such as are, or may hereafter be, appended hereto.

The embodiments of the invention in which an exclusive property or privilege is claimed are denfied as follows:

1. A segmental plate for combining with like members to define an annular wall within a cylindrical shell, said plate having oppositely facing surfaces of a configuration defining an arcuate edge subtended by a pair of radial edges converging toward each other in the direction radially inward of said arcuate edge, said configuration of said oppositely facing surfaces also defining in a first of said radial edges a notch having a flat wedge surface transverse thereto that slopes from said first radial edge progressively deeper into said plate at locations progressively more remote from said arcuate edge, and a wedge lug projecting from the second of said pair of radial edges and having a fiat wedge surface transverse to said oppositely facing surfaces and said second of said radial edges, said lug fiat wedge surface having a slope from said second edge projecting farther away therefrom at locations progressively more remote from said arcuate edge, said notch wedge surface and said lug wedge surface being spaced an equal distance from said arcuate edge and defining equal angles with the radial edge connected thereto.

2. A plate according to claim 1 having a pivot lug projecting radially outward of said arcuate edge along said first of said radial edges.

3. A plate according to claim 2 with said pivot lug having a curved edge spaced radially outward of said arcuate edge, and said curved edge having a radius smaller than the radius of said arcuate edge.

4. A plate according to claim 2 with a bracket projecting perpendicularly from one of said oppositely facing surfaces and adjacent said wedge lug, and said bracket defining therethrough a radially extending bore.

5. An annular wall comprising a plurality of segmental plates according to claim 1, the plates being arranged with the wedge lug of each plate projecting into the notch of the adjacent plate with the lug wedge surface engaging the notch wedge surface, and means connected to at least one of said plates adjacent said wedge lug for pulling said lug wedge surface radially outward relative to said notch wedge surface.

6. In a cylindrical shell, an annular wall perpendicular to said shell and comprising a plurality of plates according to claim 2, the plates being arranged with the pivot lug engaging the inner surface of the shell and the wedge lug of each plate projecting into the notch of the adjacent plate and with the lug wedge surface engaging the notch Wedge surface, and means connected to at least one of said plates and projecting outwardly through said shell for pivoting said lug Wedge surface radially outward about said pivot lug.

7. In a multiple compartment cylindrical shell rotary grinding mill a division head assembly comprising an open framework spider defining a support plane perpendicular to the shell and an annular screen on at least one side of the spider, said annular screen comprising a plurality of plates according to claim 4, the plates being arranged against the spider with the bracket projecting through said support plane, each plate is also arranged with the pivot lug engaging the inner surface of the shell and the arcuate edge of the plate spaced therefrom, the wedge lug of each plate projects into the notch of the adjacent plate with the lug wedge surface engaging the notch wedge surface, a bolt projects radially outward through at least one bracket and through said shell, and a device is attached to the projecting end of the bolt for pulling outwardly on the bolt to pivot said lug wedge surface radially outward about said pivot lug.

8. In a multiple compartment cylindrical shell rotary grinding mill a division head assembly comprising an open framework spider defining a pair of support planes perpendicular t0 the shell and an annular screen on each side of the spider, each said annular screen comprising a plurality of plates according to claim 4, the plates being arranged against one support plane of the spider with the bracket projecting through said one plane to the space Within said spider framework between said support planes, each plate is also arranged with the pivot lug engaging the inner surface of the shell and the arcuate edge of the plate spaced therefrom, the wedge lug of each plate projects into the notch of the adjacent plate with the lug Wedge surface engaging the notch wedge surface, a bolt projects radially outward through each bracket and through said shell, and a nut is attached to the projecting end of the bolt for pulling outwardly on the bolt to pivot said lug wedge surface radially outward about said pivot lug.

References Cited by the Examiner UNITED STATES PATENTS 2/1936 Ihlefeldt 241-72 XR 8/1964 Klovers 241153 XR 

1. A SEGMENTAL PLATE FOR COMBINING WITH LIKE MEMBERS TO DEFINE AN ANNULAR WALL WITHIN A CYLINDRICAL SHELL, SAID PLATE HAVING OPPOSITELY FACING SURFACES OF A CONFIGURATION DEFINING AN ARCUATE EDGE SUBTENDED BY A PAIR OF RADIAL EDGES CONVERGING TOWARD EACH OTHER IN THE DIRECTION RADIALLY INWARD OF SAID ARCUATE EDGE, SAID CONFIGURATION OF SAID OPPOSITELY FACING SURFACES ALSO DEFINING IN A FIRST OF SAID RADIAL EDGES A NOTCH HAVING A FLAT WEDGE SURFACE TRANSVERSE THERETO THAT SLOPES FROM SAID FIRST RADIAL EDGE PROGRESSIVELY DEEPER INTO SAID PLATE AT LOCATIONS PROGRESSIVELY MORE REMOTE FROM SAID ARCUATE EDGE, AND A WEDGE LUG PROJECTING FROM THE SECOND OF SAID PAIR OF RADIAL EDGES AND HAVING A FLAT WEDGE SURFACE TRANSVERSE TO SAID OPPOSITELY FACING SURFACES AND SAID SECOND OF SAID RADIAL EDGES, SAID LUG FLAT WEDGE SURFACE HAVING A SLOPE FROM SAID SECOND EDGE PROJECTING FARTHER AWAY THEREFROM AT LOCATIONS PROGRESSIVELY MORE REMOTE FROM SAID ARCUATE EDGE, SAID NOTCH WEDGE SURFACE AND SAID LUG WEDGE SURFACE BEING SPACED AN EQUAL DISTANCE FROM SAID ARCUATE EDGE AND DEFINING EQUAL ANGLES WITH THE RADIAL EDGE CONNECTED THERETO. 